The present invention relates generally to pumps for pumping liquid and, more particularly, to pumps operated by compressed air and using an injector or venturi-type nozzle to generate a vacuum therein. Pumps of this type are known, as evidenced by U.S. Pat. No. 2,141,427 to Bryant. Pumps of this type have been utilized heretofore to pump water, for example, and consist of a tank having an inlet and outlet at the bottom with one-way check valves in place at each of the inlet and outlet passageways so as to permit the passage of liquid only in one direction. At the top of the tank, a compressed air nozzle is provided spaced from an outlet exhaust pipe, both of which are placed in communication with the interior of the tank. As high pressure air is injected into the nozzle, a high velocity air stream passes from the nozzle through the exhaust passageway and causes a vacuum condition to exist within the interior of the tank. The vacuum condition causes liquid to be emitted to the tank through the inlet orifice. The one-way check valve positioned in the outlet orifice prevents stored liquid from escaping the tank while the pump is in the vacuum mode of operation. U.S. Pat. No. 2,141,427 discloses the use of a ball-type float valve which rides on the surface of the liquid within the tank. When the liquid reaches a given level within the tank, the float, through appropriate linkage, causes a gate type valve to slide across the air exhaust pipe, shutting off the flow therethrough. When the air flow is so interrupted by the gate valve, the high velocity air exhaust stream is directed downwardly into the tank, causing a positive pressure to exist therein. Consequently, the water contained in the tank is forced out through the outlet orifice at the bottom thereof. In this pressurized pump-down mode, the one-way check valve located in the inlet orifice closes to prevent any water leakage therethrough.
A further vacuum air-driven pump utilizing a venturi style nozzle is disclosed in U.S. Pat. No. 3,320,970 to McHenry. McHenry points out certain operational problems inherent in the aforementioned Bryant pump specifically associated with the operation of the float valve, such as the sticking of the float and the associated mechanical linkage. McHenry proposes an improved valve mechanism which is a liquid level responsive pressure actuator for shifting a spool-type control valve from open to closed positions so as to regulate the pumping cycle of the device. Included in the McHenry sensing system is a rather elaborate array of orifices and fine diameter tubing which render the pump suitable for operation only in very particulate-free, non-corrosive and low viscosity water environments.
The pumps of the prior art, which rely upon means positioned within the liquid accumulator tank for sensing the liquid level or pressure therein and with valve means exposed to the liquid vapors entrained in the exhausting air stream, are not suitable for use in connection with the pumping of corrosive or erosive liquids. Such corrosive liquids quickly attack the sliding metal parts and cause rapid wear and subsequent pump malfunctions. In addition, a shiftable valve spool of the type employed in U.S. Pat. No. 3,320,970 is particularly susceptible to wear caused by abrasive particulate matter present in certain slurries or corrosive vapors present in certain liquids. In addition, it is also apparent that the slidable exhaust valve and linkage of U.S. Pat. No. 2,141,427 is susceptible to abrasive wear and corrosive attack due to the exposure to entrained particulate materials and harmful vapors.
The present invention solves the problems heretofore encountered in the prior art devices for pumping corrosive and erosive liquids and abrasive slurries and the like. The present invention is constructed of corrosion resistant materials and contains no movable or sliding metal parts within the interior of the pump exposed to the liquid or vapors. In this manner, the pump of the present invention is able to withstand the rigors of long exposure to corrosive and erosive slurries, liquids and vapors, as well as solid abrasive particulates, without suffering any appreciable degradation in performance characteristics. The present invention provides a pump which is resistant to corrosive attacks from a wide range of chemical solutions, including acids, alkaline, solvents and others. Our invention provides a compact, compressed air-operated pump for reliable and durable performance having a minimum of moving parts which assures minimum downtime. The pump of the invention is inexpensive to assemble, operate and maintain in the field. The present invention further provides, in one presently preferred embodiment, a pump body constructed of a translucent material which permits visual observation of the pumping cycle while also possessing a very high hoop strength to provide superior pressure resistance.
Still further, the present invention provides a pump in which the pump in cycle and the pump down cycle times can be independently regulated to permit an infinite variety of flow rates. By increasing the pump body size, the liquid storage volume capacity is increased to permit correspondingly greater flow rates. The present invention also performs at comparable flow rates as prior pumps, but with less air consumption, resulting in energy savings for the user.